The field of human computer interaction has benefited tremendously from the use of eye-tracking technology. Eye trackers provide unique insights linking the visual and cognitive process of humans to interactions with computer devices at a level of granularity that is deeper than explicit interaction, such as mouse movements or button pushes. Eye-trackers have been used to study the usability of interfaces to improve design, identify cognitive processing challenges, and have even been used as a mechanism to interact with interfaces. In addition, eye tracking technology has been used in real-time to provide augmented cognition environments, improving overall human performance and experience.